/*
 * SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
 * Copyright (C) 1991-2000 Silicon Graphics, Inc. All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice including the dates of first publication and
 * either this permission notice or a reference to
 * http://oss.sgi.com/projects/FreeB/
 * shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * SILICON GRAPHICS, INC. BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
 * OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Except as contained in this notice, the name of Silicon Graphics, Inc.
 * shall not be used in advertising or otherwise to promote the sale, use or
 * other dealings in this Software without prior written authorization from
 * Silicon Graphics, Inc.
 */
/*
 ** Author: Eric Veach, July 1994.
 **
 */

#include "gluos.h"
#include <assert.h>
#include <stddef.h>
#include <stdio.h>
#include "mesh.h"
#include "tess.h"
#include "render.h"

#ifndef TRUE
#define TRUE 1
#endif
#ifndef FALSE
#define FALSE 0
#endif

/* This structure remembers the information we need about a primitive
 * to be able to render it later, once we have determined which
 * primitive is able to use the most triangles.
 */
struct FaceCount {
   long size; /* number of triangles used */
   GLUhalfEdge *eStart; /* edge where this primitive starts */
   void (*render)(GLUtesselator *, GLUhalfEdge *, long);
/* routine to render this primitive */
};

static struct FaceCount MaximumFan(GLUhalfEdge *eOrig);
static struct FaceCount MaximumStrip(GLUhalfEdge *eOrig);

static void RenderFan(GLUtesselator *tess, GLUhalfEdge *eStart, long size);
static void RenderStrip(GLUtesselator *tess, GLUhalfEdge *eStart, long size);
static void RenderTriangle(GLUtesselator *tess, GLUhalfEdge *eStart,
      long size);

static void RenderMaximumFaceGroup(GLUtesselator *tess, GLUface *fOrig);
static void RenderLonelyTriangles(GLUtesselator *tess, GLUface *head);

/************************ Strips and Fans decomposition ******************/

/* __gl_renderMesh( tess, mesh ) takes a mesh and breaks it into triangle
 * fans, strips, and separate triangles.  A substantial effort is made
 * to use as few rendering primitives as possible (ie. to make the fans
 * and strips as large as possible).
 *
 * The rendering output is provided as callbacks (see the api).
 */
void __gl_renderMesh(GLUtesselator *tess, GLUmesh *mesh)
{
   GLUface *f;

   /* Make a list of separate triangles so we can render them all at once */
   tess->lonelyTriList = NULL;

   for (f = mesh->fHead.next; f != &mesh->fHead; f = f->next) {
      f->marked = FALSE;
   }
   for (f = mesh->fHead.next; f != &mesh->fHead; f = f->next) {

      /* We examine all faces in an arbitrary order.  Whenever we find
       * an unprocessed face F, we output a group of faces including F
       * whose size is maximum.
       */
      if (f->inside && !f->marked) {
         RenderMaximumFaceGroup(tess, f);
         assert( f->marked);
      }
   }
   if (tess->lonelyTriList != NULL) {
      RenderLonelyTriangles(tess, tess->lonelyTriList);
      tess->lonelyTriList = NULL;
   }
}

static void RenderMaximumFaceGroup(GLUtesselator *tess, GLUface *fOrig)
{
   /* We want to find the largest triangle fan or strip of unmarked faces
    * which includes the given face fOrig.  There are 3 possible fans
    * passing through fOrig (one centered at each vertex), and 3 possible
    * strips (one for each CCW permutation of the vertices).  Our strategy
    * is to try all of these, and take the primitive which uses the most
    * triangles (a greedy approach).
    */
   GLUhalfEdge *e = fOrig->anEdge;
   struct FaceCount max, newFace;

   max.size = 1;
   max.eStart = e;
   max.render = &RenderTriangle;

   if (!tess->flagBoundary) {
      newFace = MaximumFan(e);
      if (newFace.size > max.size) {
         max = newFace;
      }
      newFace = MaximumFan(e->Lnext);
      if (newFace.size > max.size) {
         max = newFace;
      }
      newFace = MaximumFan(e->Lprev);
      if (newFace.size > max.size) {
         max = newFace;
      }

      newFace = MaximumStrip(e);
      if (newFace.size > max.size) {
         max = newFace;
      }
      newFace = MaximumStrip(e->Lnext);
      if (newFace.size > max.size) {
         max = newFace;
      }
      newFace = MaximumStrip(e->Lprev);
      if (newFace.size > max.size) {
         max = newFace;
      }
   }
   (*(max.render))(tess, max.eStart, max.size);
}

/* Macros which keep track of faces we have marked temporarily, and allow
 * us to backtrack when necessary.  With triangle fans, this is not
 * really necessary, since the only awkward case is a loop of triangles
 * around a single origin vertex.  However with strips the situation is
 * more complicated, and we need a general tracking method like the
 * one here.
 */
#define Marked(f)	(! (f)->inside || (f)->marked)

#define AddToTrail(f,t)	((f)->trail = (t), (t) = (f), (f)->marked = TRUE)

#define FreeTrail(t)	do { \
			  while( (t) != NULL ) { \
			    (t)->marked = FALSE; t = (t)->trail; \
			  } \
			} while(0) /* absorb trailing semicolon */

static struct FaceCount MaximumFan(GLUhalfEdge *eOrig)
{
   /* eOrig->Lface is the face we want to render.  We want to find the size
    * of a maximal fan around eOrig->Org.  To do this we just walk around
    * the origin vertex as far as possible in both directions.
    */
   struct FaceCount newFace = { 0, NULL, &RenderFan };
   GLUface *trail = NULL;
   GLUhalfEdge *e;

   for (e = eOrig; !Marked( e->Lface ); e = e->Onext) {
      AddToTrail( e->Lface, trail);
      ++newFace.size;
   }
   for (e = eOrig; !Marked( e->Rface ); e = e->Oprev) {
      AddToTrail( e->Rface, trail);
      ++newFace.size;
   }
   newFace.eStart = e;
   /*LINTED*/
   FreeTrail( trail);
   return newFace;
}

#define IsEven(n)	(((n) & 1) == 0)

static struct FaceCount MaximumStrip(GLUhalfEdge *eOrig)
{
   /* Here we are looking for a maximal strip that contains the vertices
    * eOrig->Org, eOrig->Dst, eOrig->Lnext->Dst (in that order or the
    * reverse, such that all triangles are oriented CCW).
    *
    * Again we walk forward and backward as far as possible.  However for
    * strips there is a twist: to get CCW orientations, there must be
    * an *even* number of triangles in the strip on one side of eOrig.
    * We walk the strip starting on a side with an even number of triangles;
    * if both side have an odd number, we are forced to shorten one side.
    */
   struct FaceCount newFace = { 0, NULL, &RenderStrip };
   long headSize = 0, tailSize = 0;
   GLUface *trail = NULL;
   GLUhalfEdge *e, *eTail, *eHead;

   for (e = eOrig; !Marked( e->Lface ); ++tailSize, e = e->Onext) {
      AddToTrail( e->Lface, trail);
      ++tailSize;
      e = e->Dprev;
      if (Marked( e->Lface ))
         break;
      AddToTrail( e->Lface, trail);
   }
   eTail = e;

   for (e = eOrig; !Marked( e->Rface ); ++headSize, e = e->Dnext) {
      AddToTrail( e->Rface, trail);
      ++headSize;
      e = e->Oprev;
      if (Marked( e->Rface ))
         break;
      AddToTrail( e->Rface, trail);
   }
   eHead = e;

   newFace.size = tailSize + headSize;
   if (IsEven( tailSize )) {
      newFace.eStart = eTail->Sym;
   }
   else if (IsEven( headSize )) {
      newFace.eStart = eHead;
   }
   else {
      /* Both sides have odd length, we must shorten one of them.  In fact,
       * we must start from eHead to guarantee inclusion of eOrig->Lface.
       */
      --newFace.size;
      newFace.eStart = eHead->Onext;
   }
   /*LINTED*/
   FreeTrail( trail);
   return newFace;
}

static void RenderTriangle(GLUtesselator *tess, GLUhalfEdge *e, long size)
{
   /* Just add the triangle to a triangle list, so we can render all
    * the separate triangles at once.
    */
   assert( size == 1);
   AddToTrail( e->Lface, tess->lonelyTriList);
}

static void RenderLonelyTriangles(GLUtesselator *tess, GLUface *f)
{
   /* Now we render all the separate triangles which could not be
    * grouped into a triangle fan or strip.
    */
   GLUhalfEdge *e;
   int newState;
   int edgeState = -1; /* force edge state output for first vertex */

   CALL_BEGIN_OR_BEGIN_DATA( GL_TRIANGLES);

   for (; f != NULL; f = f->trail) {
      /* Loop once for each edge (there will always be 3 edges) */

      e = f->anEdge;
      do {
         if (tess->flagBoundary) {
            /* Set the "edge state" to TRUE just before we output the
             * first vertex of each edge on the polygon boundary.
             */
            newState = !e->Rface->inside;
            if (edgeState != newState) {
               edgeState = newState;
               CALL_EDGE_FLAG_OR_EDGE_FLAG_DATA( edgeState);
            }
         }
         CALL_VERTEX_OR_VERTEX_DATA( e->Org->data);

         e = e->Lnext;
      } while (e != f->anEdge);
   }
   CALL_END_OR_END_DATA();
}

static void RenderFan(GLUtesselator *tess, GLUhalfEdge *e, long size)
{
   /* Render as many CCW triangles as possible in a fan starting from
    * edge "e".  The fan *should* contain exactly "size" triangles
    * (otherwise we've goofed up somewhere).
    */
   CALL_BEGIN_OR_BEGIN_DATA( GL_TRIANGLE_FAN);
   CALL_VERTEX_OR_VERTEX_DATA( e->Org->data);
   CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data);

   while (!Marked( e->Lface )) {
      e->Lface->marked = TRUE;
      --size;
      e = e->Onext;
      CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data);
   }

   assert( size == 0);
   CALL_END_OR_END_DATA();
}

static void RenderStrip(GLUtesselator *tess, GLUhalfEdge *e, long size)
{
   /* Render as many CCW triangles as possible in a strip starting from
    * edge "e".  The strip *should* contain exactly "size" triangles
    * (otherwise we've goofed up somewhere).
    */
   CALL_BEGIN_OR_BEGIN_DATA( GL_TRIANGLE_STRIP);
   CALL_VERTEX_OR_VERTEX_DATA( e->Org->data);
   CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data);

   while (!Marked( e->Lface )) {
      e->Lface->marked = TRUE;
      --size;
      e = e->Dprev;
      CALL_VERTEX_OR_VERTEX_DATA( e->Org->data);
      if (Marked( e->Lface ))
         break;

      e->Lface->marked = TRUE;
      --size;
      e = e->Onext;
      CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data);
   }

   assert( size == 0);
   CALL_END_OR_END_DATA();
}

/************************ Boundary contour decomposition ******************/

/* __gl_renderBoundary( tess, mesh ) takes a mesh, and outputs one
 * contour for each face marked "inside".  The rendering output is
 * provided as callbacks (see the api).
 */
void __gl_renderBoundary(GLUtesselator *tess, GLUmesh *mesh)
{
   GLUface *f;
   GLUhalfEdge *e;

   for (f = mesh->fHead.next; f != &mesh->fHead; f = f->next) {
      if (f->inside) {
         CALL_BEGIN_OR_BEGIN_DATA( GL_LINE_LOOP);
         e = f->anEdge;
         do {
            CALL_VERTEX_OR_VERTEX_DATA( e->Org->data);
            e = e->Lnext;
         } while (e != f->anEdge);
         CALL_END_OR_END_DATA();
      }
   }
}

/************************ Quick-and-dirty decomposition ******************/

#define SIGN_INCONSISTENT 2

static int ComputeNormal(GLUtesselator *tess, GLdouble norm[3], int check)
/*
 * If check==FALSE, we compute the polygon normal and place it in norm[].
 * If check==TRUE, we check that each triangle in the fan from v0 has a
 * consistent orientation with respect to norm[].  If triangles are
 * consistently oriented CCW, return 1; if CW, return -1; if all triangles
 * are degenerate return 0; otherwise (no consistent orientation) return
 * SIGN_INCONSISTENT.
 */
{
   CachedVertex *v0 = tess->cache;
   CachedVertex *vn = v0 + tess->cacheCount;
   CachedVertex *vc;
   GLdouble dot, xc, yc, zc, xp, yp, zp, n[3];
   int sign = 0;

   /* Find the polygon normal.  It is important to get a reasonable
    * normal even when the polygon is self-intersecting (eg. a bowtie).
    * Otherwise, the computed normal could be very tiny, but perpendicular
    * to the true plane of the polygon due to numerical noise.  Then all
    * the triangles would appear to be degenerate and we would incorrectly
    * decompose the polygon as a fan (or simply not render it at all).
    *
    * We use a sum-of-triangles normal algorithm rather than the more
    * efficient sum-of-trapezoids method (used in CheckOrientation()
    * in normal.c).  This lets us explicitly reverse the signed area
    * of some triangles to get a reasonable normal in the self-intersecting
    * case.
    */
   if (!check) {
      norm[0] = norm[1] = norm[2] = 0.0;
   }

   vc = v0 + 1;
   xc = vc->coords[0] - v0->coords[0];
   yc = vc->coords[1] - v0->coords[1];
   zc = vc->coords[2] - v0->coords[2];
   while (++vc < vn) {
      xp = xc;
      yp = yc;
      zp = zc;
      xc = vc->coords[0] - v0->coords[0];
      yc = vc->coords[1] - v0->coords[1];
      zc = vc->coords[2] - v0->coords[2];

      /* Compute (vp - v0) cross (vc - v0) */
      n[0] = yp * zc - zp * yc;
      n[1] = zp * xc - xp * zc;
      n[2] = xp * yc - yp * xc;

      dot = n[0] * norm[0] + n[1] * norm[1] + n[2] * norm[2];
      if (!check) {
         /* Reverse the contribution of back-facing triangles to get
          * a reasonable normal for self-intersecting polygons (see above)
          */
         if (dot >= 0) {
            norm[0] += n[0];
            norm[1] += n[1];
            norm[2] += n[2];
         }
         else {
            norm[0] -= n[0];
            norm[1] -= n[1];
            norm[2] -= n[2];
         }
      }
      else if (dot != 0) {
         /* Check the new orientation for consistency with previous triangles */
         if (dot > 0) {
            if (sign < 0)
               return SIGN_INCONSISTENT;
            sign = 1;
         }
         else {
            if (sign > 0)
               return SIGN_INCONSISTENT;
            sign = -1;
         }
      }
   }
   //printf("%f, %f, %f -- %d\n", norm[0], norm[1], norm[2], sign);

   return sign;
}

/* __gl_renderCache( tess ) takes a single contour and tries to render it
 * as a triangle fan.  This handles convex polygons, as well as some
 * non-convex polygons if we get lucky.
 *
 * Returns TRUE if the polygon was successfully rendered.  The rendering
 * output is provided as callbacks (see the api).
 */
GLboolean __gl_renderCache(GLUtesselator *tess)
{
   CachedVertex *v0 = tess->cache;
   CachedVertex *vn = v0 + tess->cacheCount;
   CachedVertex *vc;
   GLdouble norm[3];
   int sign;

   if (tess->cacheCount < 3) {
      /* Degenerate contour -- no output */
      return TRUE;
   }

   norm[0] = tess->normal[0];
   norm[1] = tess->normal[1];
   norm[2] = tess->normal[2];
   if (norm[0] == 0 && norm[1] == 0 && norm[2] == 0) {
      ComputeNormal(tess, norm, FALSE);
   }

   sign = ComputeNormal(tess, norm, TRUE);
   if (sign == SIGN_INCONSISTENT) {
      /* Fan triangles did not have a consistent orientation */
      return FALSE;
   }
   if (sign == 0) {
      /* All triangles were degenerate */
      return TRUE;
   }

   /* Make sure we do the right thing for each winding rule */
   switch (tess->windingRule) {
   case GLU_TESS_WINDING_ODD:
      case GLU_TESS_WINDING_NONZERO:
      break;
   case GLU_TESS_WINDING_POSITIVE:
      if (sign < 0)
         return TRUE;
      break;
   case GLU_TESS_WINDING_NEGATIVE:
      if (sign > 0)
         return TRUE;
      break;
   case GLU_TESS_WINDING_ABS_GEQ_TWO:
      return TRUE;
   }

   CALL_BEGIN_OR_BEGIN_DATA( tess->boundaryOnly ? GL_LINE_LOOP
         : (tess->cacheCount > 3) ? GL_TRIANGLE_FAN
         : GL_TRIANGLES);

   CALL_VERTEX_OR_VERTEX_DATA( v0->data);
   if (sign > 0) {
      for (vc = v0 + 1; vc < vn; ++vc) {
         CALL_VERTEX_OR_VERTEX_DATA( vc->data);
      }
   }
   else {
      for (vc = vn - 1; vc > v0; --vc) {
         CALL_VERTEX_OR_VERTEX_DATA( vc->data);
      }
   }
   CALL_END_OR_END_DATA();
   return TRUE;
}
